The present invention relates generally to the field of communications, and more particularly to communications in a cellular communication system.
In code division multiple access (CDMA) communication systems, unnecessary and excessive transmission by a user may cause interference for other users in addition to reducing the system capacity. The communication system may provide communication services that include wireless radio transmission of digitized speech, still or moving images, text messages and other types of data. An encoder in a transmitter of the communication system may receive a packet of data for encoding. Each data packet may be transmitted in a time frame. After transmitting data in each frame, the receiving destination may make a positive or negative acknowledgment of decoding the data packet. If the data packet is decoded properly, a positive acknowledgement is transmitted to the transmitting source. If the data packet is not decoded properly, a negative acknowledgement is transmitted to the transmitting source. When a negative acknowledgment is received, the transmitting source retransmits the failed data packet. The retransmission may be performed at a higher power level than the initial transmission. The increase in the power level from the initial transmission may allow the receiving destination to overcome the interference for proper decoding of the data packet. However, higher power level at the retransmission increases interference for other users. Such interference may prevent decoding of other data packets transmitted by other users. As such, increasing power level reduces system throughput and capacity and leads to an inefficient use of the communication resources.
To this end as well as others, there is a need for a method and apparatus for efficient use of communication resources in a communication system.
A method and apparatus provides for efficient use of communication resources in a CDMA communication system when a receiving destination fails to decode the packet of data. A transmitting source may be controlled for transmitting a packet of data over a data frame at a first data rate and at a power level. The transmitting source is further controlled by re-transmitting the failed packet of data at a second data rate over at least two frames of data at the initially transmitted power level. A data rate and power level selector selects the second data rate lower than the first data rate. The data rate and power level selector determines energy per bit of the packet of data at a ratio of the first and second data rates, and selects the second data rate from the ratio such that the determined energy per bit is at a minimum level.